Magnetically driven cryogen vuilleumier refrigerator

ABSTRACT

A magnetically driven cryogenic refrigeration system using the Vuilleumier cycle having hot and cold gas displacer with incorporated regenerators, each displacer positioned in a cylinder and having a permanent magnet in its base, each cylinder having an electro magnet, powered by an alternating power source located at one end and a chamber connecting the hot and cold cylinders for allowing the gas to pass between them.

United States Patent 1191 Leo [ MAGNETICALLY DRIVEN CRYOGEN VUILLEUMIER REFRIGERATOR [75] Inventor: Bruno S. Leo, Santa Monica, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Air Force, Washington, DC. 1

22 Filed: Sept. 9, 1971 21 Appl.No.: 178,866

[ Nov. 27, 1973 3,552,120 1/1971 Beale 62/6 FOREIGN PATENTS OR APPLICATIONS 185,940 3/1967 U,S.S.R 62/6 Primary Examiner-William J. Wye

' Att0rneyI-larry A. Herbert, Jr. et al.

p 57 ABSTRACT A magnetically driven cryogenic refrigeration system using the Vuilleumier cycle having hot and cold gas displacer with incorporated regenerators, each displacer positioned in a cylinder and having a pennanent magnet in its base, each cylinder having an electro magnet, powered by an alternating power source located at one end and a chamber connecting the hot and cold cylinders for allowing the gas to pass between them.

3 Claims, 3 Drawing Figures 56 63 u 4 m I I 1,,,,,,, ll N/ 21 3,, 3; 2; 21 2/ 54 We NHL 2 Sheets-Sheet ATTORNEYS M'AGNETICALLY DRIVEN CRYOGEN VUILLEUMIERREFRIGERATOR BACKGROUND OF THE INVENTION This invention relates generally to cryogenic refrigerators and more specifically to a magneticallydriven Vuilleumier refrigerator. r I

The'Vuilleumier refrigeration cycle was initially discoveredin the 'earlytwentieth century. Few'practical applications have been made inthe intervening years however, due to the factthat its efficiency is less than other knownrcryogenicrefrigeration cycles at commercial'load size applications.

Recent requirements'for miniature flightweight cryogenicrefrigerators to cool the low heat loads associated with infrared detectors and similar cryoelectronic devices coupled with some potentially inherent advantages of the cyclehave precipitated renewed interest in its evaluation. The cycle can produce cryogenic refrigeration witha source of heat as'the onlyinputrequired.

Thisconcept of utilizing heat energy in lieu of more conventional mechanical energy for'producing refrigeration may seem somewhat paradoxicalyhowever, it is inherent in the Vuilleumier cycle and'offers a number of advantages. For example, in space applications, the required heat source might beobtained via solar collector orthrough use of isotope capsule, thus-obviating the requirement for large amounts of electrical power.

All cryogenic refrigerators employ three basic processes to obtain cooling. In general, all of these -refrigeris more complicated. To accomplish this in an efficient manner the heat that is removed from the gas in cooling it to low temperature must be. added to the, gas in heating it to ambient temperature. The process is accomplished either by countercurrent heat exchanger or thermal regenerators.

In the past cryogenic refrigeratorsusing the Vuilleumier cycle have been constructed in a manner similar to that of the original conventional commercial refrigerators, that is, to use a piston and connecting rod attached to a rotating crank shaft. The crank shaft is turned with an associated motor and drive mechanism. Provided size, weight and maintenance were of little or no consideration, these refrigerators were adequate. However, in space applications these known refrigerators are limited by the aforementioned factors as well as the vibrations caused by the pistons recripicating in orthoginal planes. 7

SUMMARY OF THE INVENTION which have no mechanical interconnection. At the base -of each gas displacer is'a permanentmagnet, while" in the base of each cylinder is mounted an electro magnet. As the polarity of the electro magnets is reversed the gas'displacers are attracted or repelled and caused to move with a recipricating motion.

Since there is no connecting rod between the two displacers the hot and cold cylinders may be separated 'by a relatively large distance whereby the cold cylinder may be placed in the area to be cooled while the'hot cylindermay be. positioned at a more'convenient location.

The invention further uses an intemal-regeneration system thereby eliminating extemal hardward and'the use'of valves to control the motion of'thepistons.

It is 'thereofre an object of the invention -toprovide a 'new and improved cryogenic refrigerator.

It is another object of theinvention tojprovide anew and improved magnetically 'driven cryogenic'refrigerator.

'It is a further object of'the invention toprovide a new and improved magneticallydriven cryogenicrefrigerator that uses the Vuilleumier'cycle- -It is still another object of the invention to'p'rovidea new and improved Vuilleumier refrigerator 'that'ope'rates without motors or'drive assemblies. g

It is still a further object of theinvention to provide a new and improved cryogenic refrigerator thatgprovides motion in only one plane.

It is another object of the invention to provide'anew and improved Vuilleumier refrigerator that ontrols DESCRIPTION OF DRAWINGS FIG. 1 is a side elevational view of a typical prior art Vuilleumier cryogenic refrigerator. 7

FIG. 2 is a crossectional view of the invention in compact form. FIG. 3 is a crossectional view of the invention in elongated form.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. 1, the known prior art type of Vuilleumier refrigerator is a constant volume system wherein the geometrical working volume shown generally at 10 cannot vary because of any motion of the dis- 7 placers 12 and 14. Because of changes in the average The invention overcomes the disadvantages of the temperature of the gas that fills the working volume of the refrigerator, the pressure can and does vary as the displacer moves. Motion of the power displacer 12 toward the center of the crankshaft 16 forces gas to move from the crankcase 18, the temperature of which is approximately that of the radiator, to the hot end 20 of the power cylinder. This movement increases the average temperature ofthe gas in the working volume and hence the pressure in the fixed volume increases.

Similarly, motion of the cool displacer 14 forces some gas to leave the crankcase and flow to the cold ends 22 of the cooling cylinder. In this way the working gas is cooled and its pressure decreases.

When the crankshaft is in the position shown at 24 the pressure in the working volume assumes a high value. As the crank shaft moves in the counterclockwise direction the power displacer 12 compresses the gas since most of it is flowing into the hot cylinder volume and is absorbing heat. The cold cylinder volume is expanding and producing refrigeration because the rest of the gas is pushing the cooling displacer l4 and performing work. The result is that an amount of the working gas, is transferred to the cold end of the cooling cylinder with little change in pressure.

As the crank shaft continues to rotate and the point 24 reaches the lowest point of its travel, both of the displacers allow the gas to expand and the pressure falls to a low value. With further motion the cooling displacer l4 compresses the gas and the power displacer allows it to expand with little change in pressure. As the motion continues to point 24 and beyond, the displacers compress the gas,heat is rejected to the ambient and the pressure returns to the high value since heat is being absorbed in the hot cylinder volume 20.

The system is completed by providing a heat source 26 to heat the gas in the system. A heat exchanger 28 is connected between the hot regenerator 30 and the cold regenerator 32. The heat exchanger removes excess heat from the system to the ambient. The heat exchanger is used to remove heat from the refrigerator and heat enters the system through this exchanger.

Using the same concept of refrigeration discussed with regard to FIG. 1, the invention is shown in FIG. 2. The system consists of housing shown generally at 40, having two cylindrically shaped, opposed ends 42 and 44. Within the cylinders are gas displacers 46 and 48. The smaller displacer (46) and cylinder form the cold end of the system. Heat taken from the load on the cold end of the device is given off to the ambient through the fins 50. The cold displacer 46 is provided with a lattice like portion 52 which constitutes the cold regenerator. At the base of the cold displacer is a permanent magnet 54 in which is mounted a seal 56. The hot displacer 48 is provided with a recessed area 58 around the displacer mid-section which acts as a hot regenerator. This displacer is fitted with a permanent magnet 60.

The invention has, mesially located, a pair of electro magnets 62 and 64 that are controlled by the altemating current source 65.

' In operation the gas displacers are moved in a linear motion by the reversing fields of the electromagnets. The gas, moved by the motion of the displacers 46 and 48 passes through the chamber 66 thereby creating the proper expansion and contraction of the gas needed for refrigeration.

FIG. 3 concerns an alternative embodiment of the in- ,altemative solutions to the packaging problems inherent in space vehicles.

Having thus described my invention in detail, [present the following claims to that which I consider my invention:

l. The refrigeration apparatus comprising: a housing, including a first, hot cylinder, and a second, cold cylinder, said cylinders being interconnected to allow the passage of a fluid therebetween; means aflixed to said first cylinder for dissipating heat away from the housing; first and second fluid displacers movably positioned in said first and second cylinders and having recessed areas so shaped as to form regenerative means between said displacers and said cylinders; magnet means positioned at one end of each of the said displacers; magnet means positioned at one end at each of said cylinders; means connected to the housing for causing a magnetic interaction between said cylinders magnet means and said displacers magnet means to cause reciprocating movement of said displacers and thereby causing movement of a fluid from one cylinder to the other cylinder.

2. A system according to claim 1 wherein said magnetic means for causing motion includes a permanent magnet positioned in the base of each of the first and magnets. 

1. The refrigeration apparatus comprising: a housing, including a first, hot cylinder, and a second, cold cylinder, said cylinders being interconnected to allow the passage of a fluid therebetween; means affixed to said first cylinder for dissipating heat away from the housing; first and second fluid displacers movably positioned in said first and second cylinders and having recessed areas so shaped as to form regenerative means between said displacers and said cylinders; magnet means positioned at one end of each of the said displacers; magnet means positioned at one end at each of said cylinders; means connected to the housing for causing a magnetic interaction between said cylinders magnet means and said displacers magnet means to cause reciprocating movement of said displacers and thereby causing movement of a fluid from one cylinder to the other cyLinder.
 2. A system according to claim 1 wherein said magnetic means for causing motion includes a permanent magnet positioned in the base of each of the first and second gas displacers and a pair of electro magnets mounted in the housing.
 3. A system according to claim 2 wherein the means for controlling the motion of the gas displacers is a source of alternating current coupled to the electro magnets. 